1. Field of the Invention
This invention relates to a shearing machine which shears plates. More specifically, it relates to a shearing machine in which the thickness and width of the work piece are automatically detected. Based on these values the clearance between upper and lower blades and the rake angle are automatically adjusted, and in addition the stroke range of the ram which holds the upper blade is automatically adjusted.
2. Description of the Related Art
Previously, in order to use a shearing machine to perform good quality shearing operations with high efficiency, it was necessary to adjust the clearance between the upper and lower blades and the rake angle according to the machinability and thickness of the work piece to be sheared.
In addition, it was necessary to adjust the stroke range of the ram which holds the upper blade according to the shearing length of the work piece to prevent unnecessary shearing action beyond the end of the work piece.
Specifically, the clearance and rake angle have to be increased for work pieces of low machinability and thick work pieces to keep the necessary shearing force low, while for work pieces of short shearing length the stroke range has to be shortened so that shearing will be complete with a small amount of lowering of the ram, thus performing high quality shearing at high efficiency.
Among the characteristics of the work piece mentioned above, changes in material properties of the work piece do not occur so much and can usually be judged by usual inspection, but the thickness and shear length can change with every lot so frequent adjustment for them is necessary.
Previous shearing machines require that the work piece thickness and shear length be measured by hand everytime they changed, and then the clearance and rake angle between the upper and lower blades and the ram stroke range have to be adjusted manually according to the measured values, which was complicated and inefficient.